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| author | Fiona Klute <fiona.klute@gmx.de> | 2025-06-23 13:38:01 +0200 |
|---|---|---|
| committer | Heinrich Schuchardt <heinrich.schuchardt@canonical.com> | 2025-06-28 13:03:19 +0200 |
| commit | 97d6a2e3fe619b50303f97d0eebafaf50f1f075d (patch) | |
| tree | 9ba5ddb7008f165e6635d23aae7a1f62b5147c00 /doc/develop | |
| parent | 359e3012921f2fc2d43f3c4e320a752173f82b82 (diff) | |
doc: mention that extlinux.conf can use environment in "append"
This option is very useful for A/B boot setups with read-only
filesystems: Letting U-Boot fill in the rootfs (and possibly related
parameters) allows keeping all boot parameters except the actual slot
selection in the extlinux.conf file, where they can be updated easily.
Signed-off-by: Fiona Klute <fiona.klute@gmx.de>
Cc: Tom Rini <trini@konsulko.com>
Diffstat (limited to 'doc/develop')
| -rw-r--r-- | doc/develop/distro.rst | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst index 1d2f9c4c32b..01efce40a29 100644 --- a/doc/develop/distro.rst +++ b/doc/develop/distro.rst @@ -92,6 +92,13 @@ That said, we have some differences to these documents, namely: * If ``-`` is passed as fdt argument and ``CONFIG_SUPPORT_PASSING_ATAGS`` is enabled, then no device tree will be used (legacy booting / pre-dtb kernel). +* The ``append`` string may use environment variables. For example, an + A/B boot setup could use ``append root=PARTLABEL=root_${bootslot}`` + to set the root filesystem to the right one for the selected slot, + assuming the ``bootslot`` environment variable is set before the + extlinux.conf file is processed, and the partition is labeled to + match. + See also doc/README.pxe under 'pxe file format'. One example extlinux.conf generated by the Fedora installer is:: |